Refrigerating apparatus



y 12, 1932- R. K. MILLER REFRIGERA'IING APPARATUS INVENTOR Filed April 25, 1951 HIS ATTORNEYS.

Patented July 12, 1932 UNITED STATES PATENT OFFICE BALI H K. KILLER, OF DAYTON; OHIO, ASSIGNOB TO IBIGIDAIRE CORPORATION, OF

DAYTON, OHIO, A. CORPORATION OF DELAWARE nnrnromrmo mm'rus Application filed 'Aprfl 25,

. compression type trouble has been experifrigerant.

enced because oil employed to lubricate operating parts of the system has accumulated on the walls and on top of the liquid refrigerant within the evaporator. This accumulation of oil on the walls and within the evaporator becomes very viscous, as the temperature of the evaporator is reduced, and forms a thick layer or blanket on the refrigerant which hinders or retards evaporation of the liquid refrigerant contained in the evaporator.

The object of the present invention,is to provide heat conducting means of high thermal conductivity for conducting heat from the exterior of the evaporator directly to the liquid refrigerant to cause the liquid refrigerant to boil more readily. In carrying out my invention I provide an evaporator with a member of high heat conductivity which extends exteriorly of the evaporator and is subjected to a relatively warm medium and is arranged for conductin heat below the blanket of oil floating on tie liquid re- Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawing: 4

Fig. 1 is a vertical section through a portion of an evaporator having my invention embodied therein and having a refrigerating system shown diagrammatically adapted to be connected with the evaporator;

Fig. 2 is a vertical section through an ice cream cabinet having an evaporator constructed in accordance with my invention installed therein;

Fig. 3 is a sectional view of the evaporator taken on the lines 3-3 of Fig. 1, and

Fig. 4 is a sectional view of a portion of 1831. Serial No. 582,894.

ghe evaporator taken on the lines 44 of For the purpose of illustrating the present invention I have shown in Fig. 1 a compressor-condenser-expander type of refrigerating system having an evaporator 10 shown in section on a large scale and including connections 11 and 12 for operatively connecting the evaporator with the system. In addition to the evaporator the system includes a compressor 13, a condenser 14 and a reservoir or liquid refrigerant tank 15. Refrigerant vapor is withdrawn from the evaporator 10 through the vapor or low pressure conduit 16 and is liquefied in the condenser 14 and returned to the evaporator through the liquid or high pressure conduit 17. The compressor is operated by a motor 18 controlled by an automatic switch 19 which may be actuated in res onse to the refrigerating demand, for examp e by a pressure responslve device 21 connected to the low pressure conduit 16. It is obvious, in systems of the type disclosed, to state that the pressure-responsive device 21 which actuates the switch 19 for controlling the electric circuit to the motor is adjusted to operate betweencertain pressure limits. Since pressures and temperatures of the refrigerant increase or decrease uniformly it is apparent that the device 21 is adapted to maintain certain predetermined temperature limits within the evaporator of the system.

Referring to Fig. 1, evaporator 10 comprises a header 24 forming a reservoir for liquid refrigerant, and a plurality of ducts 25 depending from the header 24 for circulating refrigerant to a point remote from the reservoir. The liquid refrigerant indicated at 26 is kept at a constant level 27 by a valve 28 which controls a liquid refrigerant inlet opening 29. extending from the connection 11 through an end plate 30.. Valve 28 The apparatus, or system, as generally described above is lubricated by placing a quantity of oil in the crankcase of the compressorv and depending upon the splashing of the rotating parts to distribute oil throughout the compressor. Some of the oil is dissolved in the refrigerant and some of the oil is mechanically pumped by the compressor to the condenser and reservoir and eventually to the evaporator. The oil in separating by gravity from the refrigerant in the evaporator forms globules which adhere to the walls thereof and tend to remain stationary. These globules of oil form a layer of insulation between the liquid refrigerant in the evaporator and the wall thereof which insulation retards the conduction of heat from the evaporator wall to refrigerant contained therein and consequently evaporation of the refrigerant is also retarded. Finally after the refrigerant absorbs sufficient heat to cause its evaporation a disturbance occurs in the evaporator and the globules of oil are carried to the top of the liquid refrigerant. The refrigerant continues to boil oif in the evaporator, leaving the oil, which collects in a layer of from to 11/ thick on the top of the refrigerant. This layer of oil on top of the refrigerant in the evaporator becomes more viscous as the temperature of the evaporator is reduced and forms a heavy blanket on top of the refrigerant, the effect of which must be destroyed before evaporated refrigerant can enter the space above the oil so as to affect the pressure responsive device which controls the starting and stopping of the motor and compressor.

This collection or accumulation of oil in the evaporator is particularly harmful when 40 the system is used to refrigerate an ice cream cabinet or the like, wherein very low temperatures are desired to be maintained. Under such conditions within the evaporator of the system the compressor will be operated frequently and only for short intervals of time, thus causing short operating cycles of the compressor. These short cycles of the compressor are caused by the compressor creating a suction in the low pressure conduit 50 16 and in the space above the liquid level within the header 24 of the evaporator, suflicient to cause the pressure-responsive device 21 to actuate the automatic switch 19 and break the electric circuit to the motor 18, thus stopping the compressor, without breaking-up the layer of oil in the evaporator, thereby preventing liquid refrigerant below the layer of oil from vaporizing. Obviously such short cycles of the compressor will continue indefinitely and the evaporator will not be reduced to the temperature at which the pressure responsive device 21 has been set to maintain therein. Consequently the motor which drives the compressor is started an 55 abnormal number of times causing overheatirilhg thereof. Furthermore, the refrigerating e ciency of the evaporator becomes decreased, thereby permitting the temperature within the compartment in which the evaporator is located to increase. This inefilcient operation of a system will not maintain substances cooled thereby at the desired temperature and is very likely to permit the substances to deteriorate.

The foregoing mentioned diificulites occur because the walls. of evaporators are ordinarily constructed of inexpensive materials, which materials do not conduct heat as rapidly as other materials more desirable but too expensive to warrant their use. It has been found that even if the walls of an evaporator are constructed of good heat conducting material, evaporation of the refrigerant therein is retarded until a large quantity thereof vaporizes and creates a sufficient pressure to break through the heavy viscous layer of oil on top of the refrigerant. Such accumulation of vaporized refrigerant beneath the oil, until a sufficient pressure is created, causes liquid refrigerant to be 90 splashed into the gaseous refrigerant outlet leading from theevaporator when the accumulated pressure finally breaks through the layer of oil. This thereby causes refrigeration outside'of the compartment to be refrigerated and renders the system ineflicient. Such action of the refrigerant within the evaporator is caused by the large heat absorbing surfaces of the evaporator which distribute the heatthroughout the entire body of liquid refrigerant and consequently does not form suflicient pressure at any one point to break through the layer of oil, thereby permitting the temperature of the medium cooledoby the evaporator to increase above a desired limit. Thus the evaporator becomes inefficient to maintain a substantially constant lowtemperature of the medium or substance being cooled.

My invention is directed to a system whereby the heat of the medium cooled by the evaporator of the system is conducted to and concentrated at one point within the liquid refrigerant beneath the layer of oil in the evaporator and consequently the refrigerant and oil is positively agitated sufiiciently to cause the blanket or layer of oil to be broken up or to cause its blanketing effect to be destroyed. This thereby permits liquid refrigerant within the evaporator to vaporize and prevents the compressor from reducing the pressure in the space above the layer. of oil and in the low pressure conduit to a degree suflicient to effect the ressure responsive device until the desired ow temperature of the evaporator has been obtained. I provide a device which utilizes the difference in temperature of the medium to be or being cooled by the evaporator and the temperature of the liquid refrigerant within the evaporator for causing liquid refri erant to evaporate or break through the oil blanket within the evaporator.

Referring now to Fig. 1, I have provided means to destroy the blanketing effect of lubricant in an evaporator for causing the L the bar 40 extends outwardly from the wall of the header 24 and has fins or heat absorbing members 43 secured thereto for increasing the heat absorbing capacity of the bar 40. These fins 43 are also made of material of high heat conductivity and are adapted to be spaced from the walls of the evaporator so as to be disposed in the medium being cooled by the evaporator. Owing to the construction of evaporators and the difiiculties heretofore pointed out this bar or member 40 being considerably higher in temperature than the liquid refrigerant contained in the evaporator will absorb heat from the medium being cooled by the evaporator more readily than can be accomplished by walls of the evaporator and will rapidly. conduct or transmit heat to a concentrated point in the liquid refrigerant beneath the layer of oil in the evaporator and cause its evaporation and consequently agitation of the body of liquid in the evaporator.

Referring now to Fig. 2, I have shown my improved evaporator installed in an ice cream cabinet generally designated as 50. However, I do not wish to be limited to the particular installation shown for illustrating my invention. The construction and arrangement of the ice cream cabinet may be of the type fully described in a copending application of Jesse G. King, Serial No. 86,586, filed February 6, 1926. The cabinet may include insulating side and bottom walls 51 which surround a brine tank 52 containing a medium to be cooled such as a body of brine indicated as 53 for conducting heat from ice, cream can receptacles 54 to the evaporator 10. The insulated top wall 55 of the cabinet has openings therein (not shown) to permit access to the receptacles 54 which openings may be closed by covers or lids 56. The evaporator 10 is submerged in the body of brine 53 and the end portion 42 of bar or member 40 extends upwardly from the evaporator to a oint near the upper surface of the body of brine, which surface is somewhat warmer than the lower portion of the body of brine due to the thermosyphon circulation thereof.

The bar 40 thus absorbs heat from this relatively warmer portion of the brine and conducts it to the hquid refrigerant contained in the evaporator to cause evaporation thereof. Should the evaporator be very cold and oil therein tend to retard evaporation of refrigerant, whereby the medium being cooled by the evaporator will increase beyond the desired temperature limit, my improved device will ra idly transmit and concentrate the heat cause by such increase of temperature to the refrigerant in the evaporator, thereby causing'evaporation thereof to destroy the blanketing effect of lubricant floating thereon which renders the evaporator more efficient to maintain the temperature of the medium to be cooled substantially constant. 7

While I have shown a preferred form of my improved apparatus, it is thereby understood that certain modifications in construction might bemade without departing from the scope of the invention. For example, it may be desirable to make the heat conducting bar or member of rod material having a diameter of considerable greater dimension than the thickness of a wall of the header is sure in its operation and which functions efliciently when the system is operating to maintain a very low temperature, which low temperature increases the viscosit of lubricant, while at the same time provi ing means for preventing the lubricant from retarding evaporation of liquid refrigerant in the evaporator. My improved apparatus, by destroying the blanketing effect of the lubricant floating on the liquid refrigerant in the evaporator, insures positive and regular circulation of refrigerant through the evaporator and prevents violent intermittent ebullitions of the refrigerant thus preventing liquid refrigerant from being splashed into the gaseous refrigerant outlet of the evaporator. With this accomplished evaporators employed to produce very low temperatures are rendered more efficient for maintaining a constant range of temperature. Likewise the life of the compressor and its operatin motor is prolonged by the prevention of the ieretofore described short'operating cycles thereof.

While the form of embodiment of. the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming large bod the lubricant, saidineans including an element of high heat conductivity especially constructed for readily conducting heat to a concentrated point in the body of liquid refrigerant and having a part thereof extending outside the evaporator and especially constructed and positioned so that it is exposed to the temperature of the circulating medium to be cooled by the evaporator and maintained at a materially higher temperature than the liquid refrigerant in the evaporator.-

2. An evaporator of the type including a header in which .a large body of liquid refrigerant is maintained and in which a layer of lubricant floats on the liquid refrigerant, the combination of means for causing agitation ofthe refrigerant so as to destroy the blanketing efiect of the lubricant, said means including an element of'high heat conductivity especially constructed for readily conducting heat to a concentrated point in the body of liquid refrigerant and having a part thereof extending outside the header and esecially constructed and positioned so that it is exposed to the temperature of the circulating medium to be cooled by the evaporator and maintained at a materially higher temperature than the liquid refrigerant in the header.

3. An evaporator of a refrigerating system adapted to contain a body of liquid refrigerant and a layer-of oil on the refrigerant, said evaporator being positioned in a medium to be cooled thereby, means for conducting heat from said'medium to a concentrated point in the liquid refrigerant within said evaporator to agitate the refrigerant and cause the blanketing effect of the oil to be destroyed, said means including a solid member of high heat conductivity havin a portion extending outwardly from a wall 0% said evaporator into said medium and having another portion extending inwardly from a wall of the evaporator and terminating below the liquid refrigerant level in said evaporator.

4. An evaporator of a refrigerating system adapted to contain a body of liquid refrigerant and a layer ofoil on the refrigerant, said evaporator being positioned in a medium to be cooledthereby, means for conducting heat from said medium to a concentrated point in the liquid refrigerant within said evaporator to agitate v the refrigerant and cause the blanketing eflect of the oil to be destroyed, said means including a solid member of high heat conductivity having a portion extending outwardly from a wall of said evaporator into said medium and having another portion extending inwardly from a wall of the evaporator and terminating below the liquid refrigerant level in said evaporator, and means on the first mentioned portion of said member for increasing the heat absorbing capacity thereof.

-5. An evaporator of a refrigerating system adapted to contain. a body of liquid refrigerant and a layer ofvoil on the refrigerant, said evaporator being positioned in a medium to be cooled thereby, means for conducting heat from said medium to a concentrated point in the liquid refrigerant within said evaporator to agitate the refrigerant and cause the blanketing effect of the oil to be destroyed, said means including a solid member of high heat conductivity having a portion extending outwardly from a wall ofsaid evaporator into said medium and having another portion extending inwardly from a wall of the evaporator and terminating below the liquid refrigerant level in said evaporator, and a plurality of fins of high heat conductivity on the first mentioned portion of said member for increasing the heat absorbing capacity thereof.

In testimony whereof I hereto aflix my signature.

RALPH K. MILLER. 

